PA-31 involved in near midair collision while descending for approach.

Attributes
ACN	742835
Time
Date	200706
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : sbm.airport
State Reference	WI
Altitude	msl single value : 6500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : grb.tracon
Operator	general aviation : corporate
Make Model Name	PA-31 Navajo Chieftan/Mojave/Navajo T1020
Operating Under FAR Part	Part 91
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Aircraft 2
Make Model Name	Skyhawk 172/Cutlass 172
Person 1
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial pilot : cfi
Experience	flight time last 90 days : 40 flight time total : 4000 flight time type : 1200
ASRS Report	742835
Events
Anomaly	conflict : nmac
Independent Detector	other flight crewa
Miss Distance	horizontal : 50 vertical : 59
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Ambiguous

Narrative:

Cleared from 11000 ft to 4000 ft by ZAU; turned over to grb approach;' visual to mtw. I was changing radio frequency on #2 radio to monitor unicom at mtw when an object flashed at 1 O'clock position. Simultaneously warned the captain and took the controls and performed climbing right turn. Grb approach was informed and responded with no target initially then said the aircraft's transponder had just been turned on and they were at our 6 O'clock position.

Original NASA ASRS Text

Title: PA-31 INVOLVED IN NEAR MIDAIR COLLISION WHILE DESCENDING FOR APCH.

Narrative: CLRED FROM 11000 FT TO 4000 FT BY ZAU; TURNED OVER TO GRB APCH;' VISUAL TO MTW. I WAS CHANGING RADIO FREQ ON #2 RADIO TO MONITOR UNICOM AT MTW WHEN AN OBJECT FLASHED AT 1 O'CLOCK POS. SIMULTANEOUSLY WARNED THE CAPT AND TOOK THE CTLS AND PERFORMED CLBING R TURN. GRB APCH WAS INFORMED AND RESPONDED WITH NO TARGET INITIALLY THEN SAID THE ACFT'S XPONDER HAD JUST BEEN TURNED ON AND THEY WERE AT OUR 6 O'CLOCK POS.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.